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Full text of "The manufacture and properties of iron and steel"

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SEC. VII Loss in Mowing. When a Bessemer plant ^ru* ^ cupola iron, the loss is usually 10 or even 11 Per ccm "           t ^ 
rect metal the loss is nearly 10 per cent., but in Home I1-'11'1'** ^ stated to be as low as 8 per cent. Theoretically, there slum   little difference in the loss between direct and cupola, m**j ^ although silicon and manganese are lost in the cupola, ie*i inents would be burned later in the converter at any raits i i , using direct iron it is possible to work with a lower content of *u-con in the pig and thus reduce the loss. Assuming tins minimum of 8 per cent., and assuming that the carbon, silicon mid *""" ganese do not amount to more than 5 per cent., there, IB a u  -ence.of 3 per cent, of metallic iron to he accounted for. J'rt '* the metal enters the slag as shot, a separation by the magnet giving an average content of from 6 to 8 per cent., indicating a I"**  about three-quarters of 1 per cent, of the total output, and thw portion is a complete loss, as far as both product and heat HIV concerned. The large pieces of scrap in the vessel slag inny l? picked out by hand, and, as these are generally returned to lite cupolas without reweighing, they are not reckoned in the pereeitt" age of loss. The smaller particles can only he recovered by fl> rather expensive process of crushing the slag and passing it over it magnetic separator.
Another portion of iron is chemically combined with Die milieu in the slag. Experiments at Steelton on a week's run gave IW tons of vessel slag for every 1000 tons of pig-iron. This slug, itflU-r being cleaned with a magnet, averaged 15 per cent, of iron, r|>rt' senting a loss of 1.80 per cent, of the metal, but the pig-iron et*u tained 1.75 per cent, of silicon, which is higher than neei'^Hiiry, With a content of 1.00 per 'cent., the weight of slag would hvi been less, but as the bottom and lining will wear about the ^niye, the decrease in weight of slag with a decrease in, silicon is not proportional. Adding together 0.75 percent, of metal as shot and 1,8 per cent, as combined in the slag gives 2.55 per cent. agui,st H per cent, lost, indicating that one-half of one per cent, in ejecti'd from the nose in the form of dust and splashes. Some of the tiiw spray is oxidized outside the converter,, but some is burned before it passes the nose; including what actually combines with the .slig about two per cent, of metallic iron is burned inside the, Vi^sd. This figure will be used in determining the heat evolved.